"How do the sign makers know how fast I hike? distance is a known number.. you can calculate your time and speed from that."
When I did my first trek in the Mount Everest Region of Nepal, I noticed some of the trekkers would ask the Sherpa guide: "How far is it to the next village?" They expected to hear something about two miles or five miles.
Instead, the Sherpa would say "It is one day's travel to that village." --or-- "It is one half day travel to that village." That perplexed the trekkers. They could not think in terms of a distance being a half day. I figured that was just the way it was there. Part of the reason is that there are no highways, there are no cars, and there are no car odometers, so a Sherpa has very little way of knowing just how far a mile is, and the Sherpa has never seen a rolling wheel measuring a trail distance.
As it turned out, that Sherpa was wise. He knew how much time it was going to take the trekkers just from past experience. He also knew that the fast hikers were often the first ones to fail from high altitude problems.